2-ethylhexyl 12-(acetoxy)octadecanoate

Endpoint summary

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21st February 2013 - 28th March 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of relevant results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

foreskin from a single donor

Vehicle:

unchanged (no vehicle)

Details on test system:

MatTek’s patented EpiDerm tissue samples were used:

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

50 µl of the test article were applied to the top of each EpiDerm tissue. The nylon mesh was then placed on top to facilitate even distribution of the test material. The test article remained in contact with the EpiDerm tissue for 3 and 60 minutes.

Duration of treatment / exposure:

The test article remained in contact with the EpiDerm tissue for 3 and 60 minutes.

Duration of post-treatment incubation (if applicable):

At the end of the exposure period, each EpiDerm™ tissue was rinsed with phosphate buffered saline (PBS) and transferred to a 24-well plate containing 300 µI of MIT solution (1 mg/ml MIT in OMEM). The tissues were then returned to the incubator for a three-hour MTT incubation period. Following the MIT incubation period, each EpiDerm tissue was rinsed with PBS and then treated overnight with 2.0 ml of extractant solution (isopropanol) per well. The absorbency of an aliquot of the extracted MIT formazan was measured in triplicate at 540 nm using a microplate reader (µQuant Plate Reader, BioTek Instruments, Winooski, VT).

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 Min - 1st experiment

Value:

85.2

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 Min - 2nd Experiment

Value:

85.7

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 minm - 1st experiment

Value:

98.3

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 minm - 2nd experiment

Value:

99.3

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

Quality Controls:
The mean OD of the Negative Control tissues was 2.212 at 3 minutes and 2.065 at 60 minutes, which met the acceptance criterion.

The mean relative tissue viability of the 60-minute Positive Control was 3.8%, which met the acceptance criterion.

Viability differences between the two identically treated tissues in all samples and controls at 3 minutes were 0.5% to 4.5%. Viability differences between the two identically treated tissues at 60 minutes were 0.3% to 9.3%. Inter-tissue viability differences at both time points met the acceptance criterion.

Test Article Identity	viability (3 min)	viability (60 min)	Predicted corrosivity
CAS# 1365345-64-7 (SE7B Batch 2137-0)	85.5 %	98.8 %	Non - corrosive
Tissue culture water (Negative Control)	100.0 %	100.0%	Non - corrosive
Potassium Hydroxide, 8.0 N (Positive Control)	22.2 %	3.8%	Corrosive

Interpretation of results:

GHS criteria not met

Conclusions:

Based on the results of this study, the test material is not corrosive to the skin.

Executive summary:

OBJECTIVE: To predict and classify the skin corrosivity potential of a chemical by using a three dimensional human epidermis model. This protocol follows the procedures outlined in OECD Test Guideline 431, effective April 2004. METHOD SYNOPSIS: MatTek EpiDerm™ tissue samples were treated in duplicate with the test article, Negative Control and Positive Control for 3 minutes and 60 minutes. Following treatment, the viability of the tissues was determined using Methyl thiazole tetrazolium (MTT) uptake and conversion, and the absorbance of each sample was measured at 540 nm. The viability was then expressed as a percent of control values. The percent viability was used to determine corrosivity potential.

SUMMARY/CONCLUSION:

The results of the study can be seen below:

Test Article Identity	viability (3 min)	viability (60 min)	Predicted corrosivity
CAS# 1365345-64-7 (SE7B Batch 2137-0)	85.5 %	98.8 %	Non - corrosive
Tissue culture water (Negative Control)	100.0 %	100.0%	Non - corrosive
Potassium Hydroxide, 8.0 N (Positive Control)	22.2 %	3.8%	Corrosive

Based on the results of the study the test material is not corrosive. The test material will not be classified as corrosive, according to CLP.

Reference 2

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 April 2016 - 02 May 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: SE7B
Physical state/Appearance: extremely pale yellow liquid
Batch: 11547-1512D
Expiry Date: 01 August 2018
Storage Conditions: room temperature in the dark

Test system:

human skin model

Source species:

human

Details on animal used as source of test system:

EPISKIN™ Reconstructed Human Epidermis Model Kit

Vehicle:

unchanged (no vehicle)

Details on test system:

Usung an EPISKIN™ Reconstructed Human Epidermis Model Kit, the procedure followed is based on the recommended EpiSkin™ SOP, Version 1.8 (February
2009), ECVAM Skin Irritation Validation Study.
Triplicate tissues were treated with the test item for an exposure period of 15 minutes. At the end of the exposure period each tissue was rinsed before incubating for 42 hours.
Triplicate tissues treated with 10 µL of DPBS served as the negative controls and triplicate tissues treated with 10 µL of SDS 5% w/v served as the positive controls.
At the end of the post-exposure incubation period each tissue was taken for MTT-loading. The maintenance medium from beneath each tissue was transferred to pre-labeled micro tubes and stored in a freezer for possible inflammatory mediator determination. After MTT-loading a total biopsy of each epidermis was made and placed into micro tubes containing acidified isopropanol for extraction of formazan crystals out of the MTT-loaded tissues.
At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 µL samples were transferred to the appropriate wells of a pre-labeled 96-well plate. The optical density was measured at 562 nm.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

The test item was applied topically to the corresponding tissues ensuring uniform covering. 10 µL (26.3 µL/cm2) of the test item was applied to the epidermis surface.

Duration of treatment / exposure:

treatment period of 15 minutes followed by a post-exposure incubation period of 42 hours.

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

Triplicate tissues were treated with the test item for an exposure period of 15 minutes. Triplicate tissues treated with 10 µL of DPBS served as the negative controls and triplicate tissues treated with 10 µL of SDS 5% w/v served as the positive controls.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Test Item #1

Value:

101.4

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Test Item #2

Value:

95.7

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Test Item #3

Value:

106.1

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

The relative mean tissue viability for the positive control treated tissues was 8.4% relative to the negative control treated tissues and the standard deviation value of the viability was 0.7%.
The positive control acceptance criteria were therefore satisfied.
The mean OD562 for the negative control treated tissues was 0.626 and the standard deviation value of the viability was 3.2%. The negative control acceptance criteria were therefore satisfied.

The individual and mean OD562 values, standard deviations and tissue viabilities for the test item, negative control item and positive control item are given in Table 1.
The standard deviation calculated from individual tissue viabilities of the three identically test item treated tissues was 5.2%. The test item acceptance criterion was therefore satisfied

Table 1: Mean OD562Values and Viabilities for the Negative Control Item, Positive Control Item
and Test Item

Item	OD562of tissues	Mean OD562 of triplicate tissues	± SD of OD562	Relative individual tissue viability (%)	Relative mean viability (%)	± SD of Relative mean viability (%)
Negative Control Item	0.638	0.626	0.020	102.0	100∗	3.2
	0.603			96.4
	0.636			101.7
Positive Control Item	0.057	0.053	0.004	9.1	8.4	0.7
	0.049			7.8
	0.052			8.3
Test Item	0.635	0.633	0.033	101.4	101.1	5.2
	0.599			95.7
	0.664			106.1

OD = Optical Density
SD = Standard deviation
∗= The mean viability of the negative control tissues is set at 100%

Interpretation of results:

GHS criteria not met

Conclusions:

The test item was classified as non-irritant. The following classification criteria apply:
EU CLP Not classified for Irritation.
UN GHS Not classified for Irritation (category 3 can not be determined).

Executive summary:

Introduction:
The purpose of this test was to evaluate the skin irritation potential of the test item using the EPISKINTMreconstructed human epidermis model after a treatment period of 15 minutes followed by a post-exposure incubation period of 42 hours. The principle of the assay was based on the measurement of cytotoxicity in reconstructed human epidermal cultures following topical exposure to the test item by means of the colorimetric MTT reduction assay. Cell viability is measured by enzymatic reduction of the yellow MTT tetrazolium salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) to a blue formazan salt
(within the mitochondria of viable cells) in the test item treated tissues relative to the negative controls.

Method:
Triplicate tissues were treated with the test item for an exposure period of 15 minutes. At the end of the exposure period each tissue was rinsed before incubating for 42 hours. At the end of the post-exposure incubation period each tissue was taken for MTT-loading. The maintenance medium from beneath each tissue was transferred to pre-labeled micro tubes and stored in a freezer for possible inflammatory mediator determination. After MTT-loading a total biopsy of each epidermis was made and placed into micro tubes containing acidified isopropanol for extraction of formazan crystals out of the MTT-loaded tissues. At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 µL samples were transferred to the appropriate wells of a pre-labeled 96-well plate. The
optical density was measured at 562 nm. Data are presented in the form of percentage viability (MTT reduction in the test item treated tissues relative to negative control tissues).

Results:
The relative mean viability of the test item treated tissues was 101.1% after the 15-Minute exposure period and 42-Hours post-exposure incubation period (See Table 1)
Quality criteria:The quality criteria required for acceptance of results in the test were satisfied.

Conclusion:

The test item was classified as non-irritant. The following classification criteria apply:
EU CLP Not classified for Irritation.
UN GHS Not classified for Irritation (category 3 can not be determined).

Reference 3

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Read-Across Justification is attached below.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Test Item #1

Value:

101.4

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Test Item #2

Value:

95.7

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Test Item #3

Value:

106.1

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Interpretation of results:

GHS criteria not met

Conclusions:

Read-Across is claimed between BT4 (target) and SE7B (Source), according to the justification attached to the target record, and based on structural and physical/chemical similarities.

Analogue diesters (SE7B, SE6B) and BT4 contain the same functional groups, i.e the ester group adjacent to the ethylhexane side chain, and the ester group at the opposite end of the molecules. The carbon range in the main backbone of the molecules is all the same (C18) though the acetate moiety is attached at slightly different positions (C12 for BT4, C9/10 for the analogue diesters). The analogue diesters have the additional alkane chain attached to the acetate cap. The alkane chains themselves are not typically considered to be functional groups, per se, as they are relatively inactive biologically. Thus the parent molecules BT4 and the analogue diesters are similar enough to allow for read across in that there are no differences with respect to functional groups, and their only real difference is number of, and length of, saturated hydrocarbon chains.

Mammalian carboxylesterases are enzymes that are capable of metabolizing a wide variety of estercontaining substances, hydrolyzing them to their corresponding carboxylic acids and alcohols (S. Casey Laizure, 2013) (Jihong Lian, 2018). In general, carboxylesterases hydrolyze substrates to more polar molecules that are more readily excreted. The two predominant carboxylesterases in humans are most abundant in liver and gut where their function is believed to be related to first pass clearance of xenobiotics (Jihong Lian, 2018). Hydrolysis of the analogue diesters or BT4 would yield 2-ethylhexanol.

In addition, hydrolysis of BT4 would yield acetic acid plus 12-hydroxystearic acid (C18), versus either lauric acid (C12) or the coconut oil fatty acid mixture (C8-18) for SE6B and SE7B, respectively. The difference in these fatty acid chain lengths is not expected to impact toxicity of breakdown products, particularly since none of these fatty acids have been shown to be toxic, and they are in fact, commonly found in foods and used in personal care products. While fatty acids that would occur following the breakdown of the analogue diesters are known to be severe eye irritants, exposure of the eyes to the analogue diesters or BT4 would be to the parent chemicals themselves and not to
hydrolysis products. Similarly, fatty acids from the breakdown of the analogue diesters may be irritants to the skin, though expression of carboxylesterase in human skin is not expected to be significant, and exposure through skin contact would again be to the parent compounds. Breakdown of BT4 also results in acetic acid; acetic acid is of very low toxicity in humans, and is in fact a natural component in body fluids. Thus, the possibility of it occurring as a potential breakdown product from exposure to BT4 is not expected to be of toxicological concern.

Thus, toxicological data generated on any of these materials, SE6B, SE7B, and BT4, is appropriate for read-across to the other, as the variable length of the saturated hydrocarbon chain from the initial fatty acids, the slight difference in position of the acetate moiety on the fatty acid backbone, and the additional saturated hydrocarbon chain on SE6B and SE7B versus BT4 is not expected to contribute significantly to the overall toxicity profiles of the finished chemicals. Further, the difference in breakdown products, i.e. variable chain length fatty acids and additional breakdown product of acetic acid in the case of BT4, is not expected to contribute significantly to the toxicological profiles
of these chemicals. In conclusion, it is considered that toxicological data generated for either SE6B or SE7B is appropriate for read-across to BT4.

In a skin corrosion test - OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test) and a skin irritation test - OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method) the test item SE7B did not elicit any irritant or corrsive effects on the skin.
Considering the discussion above, and in view of structural similarity and low soubility of BT4, this result is also considered relevant for the read-across target BT4.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06 Mar 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of relevant results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

Not applicable as this is an in vitro study. However the bovine eyes were received from JW. Treuth & Sons, Inc. on 06 Mar 2013 and transported overnight to MB Research in Hank's Balanced Salt Solution with Pennstrep in a refrigerated container.

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

Liquids were tested undiluted. Following the pretest observations, the MEM solution was removed from the anterior chamber. A volume of 0.75 ml of the ethanol, MEM or liquid test article was applied to the epithelium of each of the three (3) positive controls, three (3) negative controls, or three (3) test articletreated corneas in a manner, which ensured the entire cornea was covered.

Duration of treatment / exposure:

10 minutes

Observation period (in vivo):

2 hours

Details on study design:

All holders and corneas were placed in a horizontal position (anterior side up) in the 32°C (± 1°C) incubator. After 10.:!:. 1 minute, the test article, ethanol or MEM solution in the controls were removed from the epithelium of the cornea and anterior chamber of the holder by washing with MEM solution containing phenol red. The anterior and posterior chambers of the holders were refilled with fresh MEM solution. Opacity measurements were made following the 10-minute exposure and MEM solution refill.

All corneas were incubated at 32°C (± 1°C) for an additional two hours at which time the MEM solution in the anterior and posterior chambers was removed and the holders refilled with fresh MEM solution. A measurement of opacity was taken with each treated cornea compared to the blank supplied with the OPKIT. This is the reading that was used in the final in-vitro calculations.

Immediately following the 2-hour opacity measurement, the MEM solution was removed from the anterior chamber and replaced with 1.0 ml of 0.4% sodium fluorescein solution (in Dulbecco's Phosphate Buffered Saline) for liquid test articles and corresponding controls. Each holder was returned to the 32°C (± 1°C) incubator in a horizontal position (anterior side up) ensuring contact of the fluorescein with the cornea.

After 90 minutes, the fluid from the posterior chamber was removed and the amount of dye, which passed through the cornea, was measured as the optical density at 490 nm by a plate reader or spectrophotometer.

Irritation parameter:

in vitro irritation score

Remarks:

Calculated in vitro score

Run / experiment:

Mean

Value:

1.43

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

Irritant / corrosive response data:
Test material - In vitro Score: 1.43
Negative Control (MEM) - In vitro score: 0.71
Positive control (ethanol) - In vitro score: 43.27

The corrected mean opacity score was 1.34. The corrected mean optical density (permeability) score was 0.006.

Interpretation of results:

GHS criteria not met

Conclusions:

The in vitro score was calculated as 1.43. The substance is not irritating

Executive summary:

Objective: To determine the potential for ocular irritation using an alternative to the Draize methodology. This protocol is based on the methodology described in the OECD Guideline for the Testing of Chemicals #437, adopted September 7,2009.

Method Synopsis: Three corneas were dosed with 0.75 ml of CAS# 1365345-64-7 (SE7B Batch 2137-0). Opacity measurements and sodium fluorescein permeability were determined.

Summary: The corrected mean opacity score was 1.34. Controls were within normal limits. The corrected mean optical density (permeability) score was 0.006.

Conclusion: The in vitro score was calculated as 1.43.

Reference 2

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Read-Across Justification is attached below.

Reason / purpose for cross-reference:

read-across source

Irritation parameter:

in vitro irritation score

Remarks:

Calculated in vitro score

Run / experiment:

Mean

Value:

1.43

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Interpretation of results:

GHS criteria not met

Conclusions:

Read-Across is claimed between BT4 (target) and SE7B (Source), according to the justification attached to the target record, and based on structural and physical/chemical similarities.

Analogue diesters (SE7B, SE6B) and BT4 contain the same functional groups, i.e the ester group adjacent to the ethylhexane side chain, and the ester group at the opposite end of the molecules. The carbon range in the main backbone of the molecules is all the same (C18) though the acetate moiety is attached at slightly different positions (C12 for BT4, C9/10 for the analogue diesters). The analogue diesters have the additional alkane chain attached to the acetate cap. The alkane chains themselves are not typically considered to be functional groups, per se, as they are relatively inactive biologically. Thus the parent molecules BT4 and the analogue diesters are similar enough to allow for read across in that there are no differences with respect to functional groups, and their only real difference is number of, and length of, saturated hydrocarbon chains.

Mammalian carboxylesterases are enzymes that are capable of metabolizing a wide variety of estercontaining substances, hydrolyzing them to their corresponding carboxylic acids and alcohols (S. Casey Laizure, 2013) (Jihong Lian, 2018). In general, carboxylesterases hydrolyze substrates to more polar molecules that are more readily excreted. The two predominant carboxylesterases in humans are most abundant in liver and gut where their function is believed to be related to first pass clearance of xenobiotics (Jihong Lian, 2018). Hydrolysis of the analogue diesters or BT4 would yield 2-ethylhexanol.

In addition, hydrolysis of BT4 would yield acetic acid plus 12-hydroxystearic acid (C18), versus either lauric acid (C12) or the coconut oil fatty acid mixture (C8-18) for SE6B and SE7B, respectively. The difference in these fatty acid chain lengths is not expected to impact toxicity of breakdown products, particularly since none of these fatty acids have been shown to be toxic, and they are in fact, commonly found in foods and used in personal care products. While fatty acids that would occur following the breakdown of the analogue diesters are known to be severe eye irritants, exposure of the eyes to the analogue diesters or BT4 would be to the parent chemicals themselves and not to
hydrolysis products. Similarly, fatty acids from the breakdown of the analogue diesters may be irritants to the skin, though expression of carboxylesterase in human skin is not expected to be significant, and exposure through skin contact would again be to the parent compounds. Breakdown of BT4 also results in acetic acid; acetic acid is of very low toxicity in humans, and is in fact a natural component in body fluids. Thus, the possibility of it occurring as a potential breakdown product from exposure to BT4 is not expected to be of toxicological concern.

Thus, toxicological data generated on any of these materials, SE6B, SE7B, and BT4, is appropriate for read-across to the other, as the variable length of the saturated hydrocarbon chain from the initial fatty acids, the slight difference in position of the acetate moiety on the fatty acid backbone, and the additional saturated hydrocarbon chain on SE6B and SE7B versus BT4 is not expected to contribute significantly to the overall toxicity profiles of the finished chemicals. Further, the difference in breakdown products, i.e. variable chain length fatty acids and additional breakdown product of acetic acid in the case of BT4, is not expected to contribute significantly to the toxicological profiles
of these chemicals. In conclusion, it is considered that toxicological data generated for either SE6B or SE7B is appropriate for read-across to BT4.

In an OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants), the in vitro score for test item SE7B was calculated as 1.43. The substance is not irritating to the eye.
Considering the discussion above, and in view of structural similarity of BT4, this result is also considered relevant for the read-across target BT4.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Read-Across is claimed between BT4 (target) and SE7B (Source), according to the justification attached to the target record, and based on structural and physical/chemical similarities.

Analogue diesters (SE7B, SE6B) and BT4 contain the same functional groups, i.e the ester group adjacent to the ethylhexane side chain, and the ester group at the opposite end of the molecules. The carbon range in the main backbone of the molecules is all the same (C18) though the acetate moiety is attached at slightly different positions (C12 for BT4, C9/10 for the analogue diesters). The analogue diesters have the additional alkane chain attached to the acetate cap. The alkane chains themselves are not typically considered to be functional groups, per se, as they are relatively inactive biologically. Thus the parent molecules BT4 and the analogue diesters are similar enough to allow for read across in that there are no differences with respect to functional groups, and their only real difference is number of, and length of, saturated hydrocarbon chains.

Mammalian carboxylesterases are enzymes that are capable of metabolizing a wide variety of estercontaining substances, hydrolyzing them to their corresponding carboxylic acids and alcohols (S. Casey Laizure, 2013) (Jihong Lian, 2018). In general, carboxylesterases hydrolyze substrates to more polar molecules that are more readily excreted. The two predominant carboxylesterases in humans are most abundant in liver and gut where their function is believed to be related to first pass clearance of xenobiotics (Jihong Lian, 2018). Hydrolysis of the analogue diesters or BT4 would yield 2-ethylhexanol.

In addition, hydrolysis of BT4 would yield acetic acid plus 12-hydroxystearic acid (C18), versus either lauric acid (C12) or the coconut oil fatty acid mixture (C8-18) for SE6B and SE7B, respectively. The difference in these fatty acid chain lengths is not expected to impact toxicity of breakdown products, particularly since none of these fatty acids have been shown to be toxic, and they are in fact, commonly found in foods and used in personal care products. While fatty acids that would occur following the breakdown of the analogue diesters are known to be severe eye irritants, exposure of the eyes to the analogue diesters or BT4 would be to the parent chemicals themselves and not to

hydrolysis products. Similarly, fatty acids from the breakdown of the analogue diesters may be irritants to the skin, though expression of carboxylesterase in human skin is not expected to be significant, and exposure through skin contact would again be to the parent compounds. Breakdown of BT4 also results in acetic acid; acetic acid is of very low toxicity in humans, and is in fact a natural component in body fluids. Thus, the possibility of it occurring as a potential breakdown product from exposure to BT4 is not expected to be of toxicological concern.

Thus, toxicological data generated on any of these materials, SE6B, SE7B, and BT4, is appropriate for read-across to the other, as the variable length of the saturated hydrocarbon chain from the initial fatty acids, the slight difference in position of the acetate moiety on the fatty acid backbone, and the additional saturated hydrocarbon chain on SE6B and SE7B versus BT4 is not expected to contribute significantly to the overall toxicity profiles of the finished chemicals. Further, the difference in breakdown products, i.e. variable chain length fatty acids and additional breakdown product of acetic acid in the case of BT4, is not expected to contribute significantly to the toxicological profiles

of these chemicals. In conclusion, it is considered that toxicological data generated for either SE6B or SE7B is appropriate for read-across to BT4.

In a skin corrosion test - OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test) and a skin irritation test - OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method) the test item SE7B did not elicit any irritant or corrsive effects on the skin.

In an OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants), the in vitro score for test item SE7B was calculated as 1.43. The substance is not irritating to the eye.

Considering the discussion above, and in view of structural similarity and low soubility of BT4, these results are also considered relevant for the read-across target BT4.